CVE-2023-0926 in Custom Permalinks Plugin
Summary
by MITRE • 08/24/2024
The Custom Permalinks plugin for WordPress is vulnerable to Stored Cross-Site Scripting in versions up to, and including, 2.6.0 due to insufficient input sanitization and output escaping on tag names. This allows authenticated users, with editor-level permissions or greater to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page, even when 'unfiltered_html' has been disabled.
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Analysis
by VulDB Data Team • 03/13/2025
The Custom Permalinks plugin for WordPress presents a critical security vulnerability classified as CVE-2023-0926, affecting all versions up to and including 2.6.0. This vulnerability manifests as a stored cross-site scripting flaw that exploits insufficient input sanitization and output escaping mechanisms within the plugin's handling of tag names. The flaw specifically targets the plugin's inability to properly validate and sanitize user-supplied data before storing it in the WordPress database, creating a persistent vector for malicious code injection that can affect any user who accesses the compromised pages.
The technical implementation of this vulnerability stems from the plugin's failure to adequately sanitize tag names that are submitted by authenticated users. When editors or users with equivalent privileges create or modify custom permalinks containing specially crafted malicious scripts within tag names, these inputs are stored directly in the WordPress database without proper sanitization. The vulnerability is particularly concerning because it operates outside the normal WordPress security boundaries that typically protect against script execution, even when the 'unfiltered_html' capability has been properly disabled for most users. This allows attackers with editor-level permissions to bypass standard content filtering mechanisms and inject persistent malicious scripts that execute in the context of any user who views the affected pages.
The operational impact of CVE-2023-0926 extends beyond simple script injection, as it represents a privilege escalation vulnerability that can be leveraged by malicious actors within the WordPress ecosystem. An attacker with editor-level permissions can craft malicious tag names containing javascript payloads that will execute whenever any user accesses the affected pages, potentially leading to session hijacking, credential theft, or further exploitation of the compromised WordPress installation. This vulnerability directly maps to CWE-79 which describes cross-site scripting flaws, and aligns with ATT&CK technique T1566.001 for initial access through spearphishing attachments, as the malicious scripts could be used to establish further footholds within the compromised environment. The stored nature of the vulnerability means that the malicious payloads persist indefinitely until manually removed, creating a long-term threat vector that can affect users for extended periods.
Mitigation strategies for CVE-2023-0926 should focus on immediate plugin updates to versions that address the sanitization and escaping vulnerabilities, as well as implementing additional access controls to limit the scope of users who can modify permalinks. Organizations should conduct thorough audits of their WordPress installations to identify all instances of the vulnerable plugin and ensure proper patching procedures are followed. Network monitoring should be enhanced to detect potential exploitation attempts, and administrators should consider implementing additional security layers such as web application firewalls to detect and block malicious script payloads. The vulnerability also highlights the importance of input validation and output escaping principles in WordPress plugin development, emphasizing the need for proper security testing and code review processes that align with industry standards and best practices for preventing cross-site scripting attacks.